Just finished juxt. It's one of my favorites. Perhaps my favorite use is computing the coordinates on a unit circle given an input in radians:

(def unit-coordinates (juxt #(Math/cos %) #(Math/sin %)))

(defn map-vals [f m]
  (->> m
       (map (juxt key (comp f val)))
       (into (empty m))))

(map-vals inc {:a 1 :b 2})
=> {:a 2, :b 3}

I see myself using the latter more. The former is cool, but I don't finding myself doing geometry as much as I'd like.